<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<canvas id="canvas" width="600" height="600" style="border: 2px solid; display: block;  margin: 50px auto">
    你的浏览器不支持七巧板
</canvas>
</body>


<script type="text/javascript">


    window.onload = function(){
        var other.canvas =  document.getElementById("canvas");
        var context = canvas.getContext("2d");
        context.arc(300,300,100,0,0.5*Math.PI,true);
        context.fillStyle="orange";
        context.fill();

    }

</script>
</html>